signal_ios_arm64.s

Documentation: runtime/cgo

     1// Copyright 2015 The Go Authors. All rights reserved.
     2// Use of this source code is governed by a BSD-style
     3// license that can be found in the LICENSE file.
     4
     5#include "textflag.h"
     6
     7// xx_cgo_panicmem is the entrypoint for SIGSEGV as intercepted via a
     8// mach thread port as EXC_BAD_ACCESS. As the segfault may have happened
     9// in C code, we first need to load_g then call xx_cgo_panicmem.
    10//
    11//	R1 - LR at moment of fault
    12//	R2 - PC at moment of fault
    13TEXT xx_cgo_panicmem(SB),NOSPLIT|NOFRAME,$0
    14	// If in external C code, we need to load the g register.
    15	BL  runtime·load_g(SB)
    16	CMP $0, g
    17	BNE ongothread
    18
    19	// On a foreign thread.
    20	// TODO(crawshaw): call badsignal
    21	MOVD.W $0, -16(RSP)
    22	MOVW $139, R1
    23	MOVW R1, 8(RSP)
    24	B    runtime·exit(SB)
    25
    26ongothread:
    27	// Trigger a SIGSEGV panic.
    28	//
    29	// The goal is to arrange the stack so it looks like the runtime
    30	// function sigpanic was called from the PC that faulted. It has
    31	// to be sigpanic, as the stack unwinding code in traceback.go
    32	// looks explicitly for it.
    33	//
    34	// To do this we call into runtime·setsigsegv, which sets the
    35	// appropriate state inside the g object. We give it the faulting
    36	// PC on the stack, then put it in the LR before calling sigpanic.
    37
    38	// Build a 32-byte stack frame for us for this call.
    39	// Saved LR (none available) is at the bottom,
    40	// then the PC argument for setsigsegv,
    41	// then a copy of the LR for us to restore.
    42	MOVD.W $0, -32(RSP)
    43	MOVD R1, 8(RSP)
    44	MOVD R2, 16(RSP)
    45	BL runtime·setsigsegv(SB)
    46	MOVD 8(RSP), R1
    47	MOVD 16(RSP), R2
    48
    49	// Build a 16-byte stack frame for the simulated
    50	// call to sigpanic, by taking 16 bytes away from the
    51	// 32-byte stack frame above.
    52	// The saved LR in this frame is the LR at time of fault,
    53	// and the LR on entry to sigpanic is the PC at time of fault.
    54	MOVD.W R1, 16(RSP)
    55	MOVD R2, R30
    56	B runtime·sigpanic(SB)
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